Media format

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Media format - PowerPoint PPT Presentation

Media format

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Presentation Transcript

1. Media format Last updated on June 15, 2010 Doug Young Suh suh@khu.ac.kr Media signal

2. Go to basics • “I learned everything in Kindergarten.” • What did I learn in Kindergarten for video coding? • Probability theory, linear algebra, sampling theory

3. AD conversion Analog = continuous time + analog Digital = discrete time + digital Media signal

4. Sampling and human-being • Sampling theory (Nyquist theory) Sampling frequency fs > 2fmax • Speech 8kHz > 2 X 3.2kHz • Audio 44.1kHz > 2 X 20kHz • Video • Temporal : 24Hz (movie), 60Hz (TV) • Spatial 440Hz, A, Ra Low freq. Do-Re-Mi-Pa-Sol-Ra-Si-Do High frequency Media signal

5. Quantization • Analog digital • Analog : infinite number of values • Digit-al : finite number of values Media signal

6. Quantization and de-quantization • Loss of information, but acceptable accuracy Media signal

7. Image Resolution • Original image :256*256, 8bits 128*128, 8bits 256*256, 4bits Media signal

8. Color representation • RGB cf) rectangular coordinate • YCbCr (YUV) cf) polar coordinate Red (255,0,0) Blue (0,0,255) Media signal

9. Color representation • Original Red Green Blue 4:4:4 • Y U V • U, V no high freq.  4:2:2  4:2:0

10. Color conversion • 1 to 1 mapping • RGBYCbCr • Y = 0.29900R+0.58700G+0.11400B • Cb = -0.16874R-0.33126G+0.50000B • Cr = 0.50000R-0.41869G-0.08131B • YCbCrRGB • R=1.00000Y+1.40200Cr • G=1.00000Y-0.34414Cb-0.71414Cr • B=1.00000Y+1.77200Cb Media signal

11. Color conversion • 4:4:4  1+1+1 • 4:2:2 Horizontally 2:1 subsampling • 4:2:0 1+1/4+1/4 • Most popular • Amount ½ Media signal

12. Video formats • QCIF  CIF(352x288)  4CIF • QVGAVGA(640x480)SXGA(1280x1024)

13. Video encoding 2-1 2-3 2-2 Original Video + DCT Q VLC Encoded Bitstream IQ Motion vector Motion Estimation Frame Memory IDCT Networked Video